1. Field of the Invention
The present invention relates to a resonator making use of mechanical resonance, an oscillator using the resonator, and a communication device provided with the oscillator.
2. Description of the Related Art
With recent advancement in wireless communication technology, communication instruments using the wireless communication technology are requested to reduce their size and weight. Micro-electromechanical system (MEMS) technology, capable of fabricating fine mechanical structures based on micro-processing technology used for semiconductor processing, has been adopted for processing of RF signal processor unit which has been difficult to downsize.
As one example, mechanical resonator making use of mechanical resonance is known. RF elements using the mechanical resonator, such as filter, oscillator and mixer, are expected to be applied to the field of communication, because they are small in size and can be integrated. Japanese Patent Application Publication No. JP 2006-33740 (Patent Document 1) and U.S. Pat. No. 6,249,073 (Patent Document 2) disclose technologies of mechanical resonators.
Small insertion loss and high Q-value of resonator are required for fabricating an oscillator by use of the resonator. Since the mechanical resonator has high impedance, it is necessary to connect the same resonating elements in parallel, that is, to lower the impedance by parallel connection, whereas the parallel connection results in decrease in the Q-value of resonator.